An Interpenetrated Metal-Organic Framework and Its Gas Storage Behavior: Simulation and Experiment

A new metal organic framework, called UHM-6 (UHM: University of Hamburg Materials), based on the copper paddle wheel motif and a novel organosilicon linker, 4',4 ''(dimethylsilanediyl)bis(biphenyl-3,5-dicarboxylic acid) (sbbip), has been synthesized and characterized with regard to its gas storage behavior up to 1 bar for hydrogen, methane, and carbon dioxide. The 2-fold interpenetrated microporous framework of UHM-6 is isoreticular to PMOF-3 (Inorg. Chem. 2009, 48, 11507) and is composed of cuboctahedral cages of Cu-2 paddle wheels connected via nonlinear organosilicon units. The structure (SG 1422, No. 97) is characterized by straight channels running along the [001] and [110] direction. UHM-6 reveals a specific surface area of S-BET similar to 1200 m(2) g(-1) and a specific micropore volume of V-micropore similar to 0.48 cm(3) g(-1). At 1 bar the activated form of UHM-6 shows a hydrogen uptake of 1.8 wt % (77 K), a methane uptake of 0.8 mmol g(-1) (293 K), and a carbon dioxide uptake of 3.3 mmol g(-1) (273 K). Accompanying theoretical grand-canonical Monte Carlo (GCMC) simulations show an overall good agreement with the experimental results. Furthermore, GCMC adsorption simulations for three binary equimolar mixtures (CH4/H-2, CO2/H-2, and CO2/CH4) were carried out (T = 298 K) to assess the potential for gas separation/purification applications.